EclipseWriter: Make it fit to write the Norne dataset

in particular, this involved fixing the active cells management and
the possibility to use it without an EclipseGridParser object. This
patch also cleans up the code a bit (mainly for the paths which use
the new parser) so that the operations which are done on a data field
are not mingled into method arguments anymore...
add variants of all methods which take a deck of the new parser to the well handling code

this is supposed to be a temporary work around for not requiring the
old parser. Most of this code can be removed after the new well
handling code has landed. (which might be still some time, alas.)
some hacks which are currently required to make the Norne deck work

... at least for some definition of "work".